The invention relates to a method of determining a property of a layer of a phosphor screen on a substrate. Said layer may be applied, for example, to the inner surface of a display window of a display device, for example the inner surface of a display window of a cathode ray tube, or to a lamp.
Cathode ray tubes are used, inter alia, in television receivers and computer monitors. Lamps are used in lighting devices.
Display devices, such as cathode ray tubes and plasma display apparatuses, comprise a phosphor screen on an inner surface of a display window. A phosphor screen comprises a number of layers, for example three phosphor layers (red, green and blue), a so-called black matrix layer and, sometimes, color filter layers. The quality of the image displayed by the display device is determined to a substantial degree by the properties of these layers. A method of determining a number of properties of phosphor layers in a cathode ray tube is disclosed, for example, in the English-language abstract of Japanese patent application 08-162023. The position of the phosphor layers is determined by means of optical measurements.
Phosphor layers are also applied to the inner surface of lamps. The quality of the lamps depends on the quality of the applied phosphor layer.
However, a number of properties and, in particular, the thickness of a layer cannot be measured by means of the known method. Hitherto, the thickness is customarily measured by making an incision in a phosphor layer whereafter the thickness is measured. However, this measuring method is destructive, which leads to higher costs and which also means that it is impossible to test a product which is to be sold.
It is an object of the invention to provide a method which enables properties of a layer of a phosphor screen on a substrate, for example the inner surface of a display window of a display device or a lamp, to be determined in a non-destructive manner.